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Home✈️Aircraft🚁HelicopterAutogyros - Gyrocopters › scratch building a gyro questions
09-07-2006 08:06 PM  14 years ago
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eyeflyhelis

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charlotte nc

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scratch building a gyro questions
gave it some thought and i think im going to try to scratch build agyro from extra stuff i have around. i have a e-flite 370 motor with 25a esc and some t-rex blades plus lots of balsa. anyone have any tips before i start this adventure? i think i can get it in the air this weekend but i need some ideas on attaching the rotors. could use a triangle block on top but need main shaft options & attaching to the main. i have a few straight spare t-rex mains & bearings.?????
how tail do i want the mast from the fuseluge?
only you have the power to make no difference!
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09-07-2006 08:07 PM  14 years ago
eyeflyhelis

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got some 30 size baldes also and a main shaft with bearing for a 30 size ship.only you have the power to make no difference!
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09-07-2006 08:08 PM  14 years ago
eyeflyhelis

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do i want 3 blades like most of those other kits or is 2 fine? there are 3 gyros at my local airport and they all have 2 blades.
i was not going to make a predrive for it - just give it a spin by hand to start it off.
only you have the power to make no difference!
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09-07-2006 08:09 PM  14 years ago
eyeflyhelis

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found some brushed 370 size motors also so i guess i could make a predrive, think i need one?only you have the power to make no difference!
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09-07-2006 08:10 PM  14 years ago
eyeflyhelis

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ok ikeep digging in my supplies nd i found enough styrofoam board to build one out of that instead of balsa. i could reinforce it with a few pieces of balsa or carbon rodsonly you have the power to make no difference!
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09-09-2006 11:38 PM  14 years ago
imsofaman

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Hmmmmm. Sounds like a fun project. Three blades are ususally used for like a flex rotor plate like my gyro (DAG-1). Two blades...usually are used when using a swash plate system. Do you have an old heli that you could use the blade and main rotor system?
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09-10-2006 01:40 AM  14 years ago
eyeflyhelis

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i have two spare raptor and one spare hawk swash plate up. but almost all the gyros i know of in 'real life' dont have a collective system. they gain there speed by forward momentum.
?????
only you have the power to make no difference!
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09-10-2006 03:24 PM  14 years ago
imsofaman

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You can have a lot of fun with a collective. You can vary your pitch on the fly. The swash makes for the cyclitic movement of the blades which is awesome. Some guys rave over it. It is the same as the helicopter with the swash moving the tilt the pitch of the blade at certain points as the rotors spin. You can set the pitch static if you like. Set them at minus 1 degree and use wood blades with a Clark Y profile. That will produce you spin up when moving forward and once at max. rpm.....the Clark Y profile produces lift.

Hints on take off:

If you see a model gyro or even the real thing roll to the side on take off.....that means the rotors are not up to max. RPM. The lift is only being produced on the side of the left or right side of the rotor's circular path. At full RPM, the gyro will lift off like an airplane with no tilting to the side. Even on my last video I made....you can see it roll to the left.....I set it back down and increase throttle to full and it smoothed out and took off straight.

Send some photos of what you have....
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09-11-2006 01:40 AM  14 years ago
eyeflyhelis

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can you send me the links to your vids or are they on hte other post?
my pics will be a few days out im in rough stages still and time is not on my side lately.
only you have the power to make no difference!
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09-11-2006 01:57 AM  14 years ago
imsofaman

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09-11-2006 03:06 AM  14 years ago
Gyronut

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Sofaman

Your comment that lift is not produce on the retreating blade is totally incorrect.

Of course there is lift produced but there is more of it on the advanceing blade because of the higher airspeed.

This is called disymetry of lift and is countered by use using a flapping rotor head design.

BTW: why weren't you at the annual "Gyronuts" flyin...???

Regards

Gyronut
AKA Gyronuts.com
Rick
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09-11-2006 03:57 AM  14 years ago
imsofaman

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No....I was not at the fly in. I wish I had more vacation time.

My blades turn counter clock wise, when I give it too much throttle too quick it ALWAYS rolls to the left. A little more patience and time the rotors hit their peak RPM and it takes off straight. Every gyro I have does the same.
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09-11-2006 04:08 AM  14 years ago
imsofaman

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Your comment that lift is not produce on the retreating blade is totally incorrect.
By the way....here is a quote from Jim Baxter's page. You may want to refer to his page for "correct" information.

"I just installed a flex hinged hub, and the model wants to roll to the left on launch.... Any idea as to the problem?"

"If your rotor rotates CCW (left when viewed from the top), one strong possibility is insufficient "up" flap (up flex) allowance in the blades. If you only have perhaps 10 degrees or less originally, increase this to a good 20 degrees and re-test the rotor and model. Note: This assumes you are allowing the rotor to reach full autorotational RPM, and are not attempting to "pull" the model off the ground prematurely. Because if the rotor is not up to full rpm for safe launch, it will probably roll into the retreating rotor blade."

The retreating blades is moving to the left....it rolls to the left... when not at the full or autorotational speed.

http://www.autogyro.com
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09-11-2006 04:23 AM  14 years ago
imsofaman

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09-11-2006 05:34 AM  14 years ago
eyeflyhelis

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well im actualy a full scale helicopter/ airplane pilot and retreating blade stall is the lack of lift on the retreating blade. on a helicopter it can be caused by going to fast on a gyro not fast enough. i asked a few of the real gyro pilots at my field about the retreating blade stall and they told me you cant over speed the rotors on a gyro. maybe so but i would have to disagree- vne?? just for stress on component failure? on helicopter its a few knots below blade stall so you dont risk the enevitable high speed roll (easily corected on a heli)- actual you feel a shake before it happens not a big deal.
back to gyro's i understand about blade stall and the 'shutter' or flapping of the wings but i thought as long as you have speed the gyro would eventually leave the ground. but if they are schecty handleing then i guess you would have tendency to rotate faster to get offthe wheels? any opinions?
only you have the power to make no difference!
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09-11-2006 05:44 AM  14 years ago
eyeflyhelis

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oh yeah almost forgot why i came back-
is there some formula to how big (long)the rotors need to be to size of the fuselage?
or blade wieght to fuselage or complete ship wieght?
i think the collective will not work with the one im piecing together cuase i basicaly building a modified slowstick.
i started out with a much bigger ideawhich kept scaling down as i started to ad more expensive parts. minus rx and speed control i think im going to have this built for less than $30 counting servos!
but if it works well its a learning bed so i can go bigger and bigger.

blades
i was going to us 30 size blades but so far my whole ship is under 15oz.\
so now im wondering if i can pull off using t-rex stock blades (plastic).- since they such anyways why not try them here maybe they would work well or well enough? i believe they are symetrical.
helicopter blades center themselves once power evens out. will a gyro blades also or do i need to mount them stiffly?

im using a cheap brushed motor until it proves airworthy- then brushless-
only you have the power to make no difference!
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09-11-2006 11:25 AM  14 years ago
imsofaman

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09-11-2006 06:09 PM  14 years ago
eyeflyhelis

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charlotte nc

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thanks lots of good info on that site.
just designed my rotor head and its a lot simpler than i started out with.
only you have the power to make no difference!
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09-11-2006 06:15 PM  14 years ago
eyeflyhelis

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charlotte nc

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my rotor head design: ok copy but slightly modified design

im goingto use a control service hinge (heavy duty) and resupoort the sides with light plywood. then im going to run a stiff solid piece or rod into it from the rear- for pitch control- and the same rod throught it laterialy for alerion control.
going to cut some plastic coffee can lids up for my rotor head. going to shape some wood like my blade holder and leave it about 2-4 mm short of the blades.
will use a long skinny bolt with nuts on the top of the hinge and one ontop of the head. will use a bearing from a r/c helicopter in the center.
only you have the power to make no difference!
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09-11-2006 06:21 PM  14 years ago
eyeflyhelis

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charlotte nc

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blades??
still not sure of blade wirghts got a good idea on length but not some much about wieghts.
does it work like a helicopter? lighter blade faster responce less stability and quicker spool up?- but also spools down faster- less inertia.
or am i looking at it the wrong way?

i no longer plan to use helicopter blades but to take some balsa and cut it down to lenght and then shape the top o and nice arch-leaving the bottom flat. i have clear blade covering so i can make the blades up to 3" wide. I planned to go around 2 1/2 " wide.

i figured wider blades create more lift which = less speed on take of.
got another friend who is thinking about building a gyro now too but he's going the kit route.- i like the challenage....
only you have the power to make no difference!
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